Electric Brake Problem

riche789 wrote:
The electric brakes on my 30 foot travel trailer are not providing much braking for the rig. I have started doing some troubleshooting related to the voltage and current.

I have only 4 amps total for the dual axle trailer and only 1 amp at each of the magnets.

Says the problem is/are poor connections and/or high resistance
connection to undersized wiring...all so common on trailer wiring

The voltage to one of the magnets was 10.9 volts with the controller set at 5 out of 10. I repaired some wires with damaged insulation, but only gained a few tenths of an amp for the four wheels.

There should NOT be that much voltage drop. Again, indicative of poor
connections and/or too small wire gauge

I pull a second smaller trailer with a single axle and the brakes there work very well. In fact I have to turn the controller way down to keep braking smooth.

Not sure how to proceed.

Maybe pull new wires?

Thanks for any ideas!

Recommend rewiring the trailer brakes and anything else you might
wish to re-do while down there with all the tools and materials at hand

This is the best write up I've come across and is by our admin LAdams

I rewired my trailer brakes

LAdams wrote:



I tow a large heavy trailer (about 34' overall and #9400 loaded)... I haven't really been satisfied with it's braking ability from the day I received it, so I started going over things a few weeks ago...

In addition to finding numerous questionable connections, I found that the main brake lead wire on the TT was only 14 Gauge and the crossover wires that runs across the axles was even less than that maybe 16 gauge, perhaps less...

After adjusting the brakes and readjusting my Jordan controller, things were better but still not as good as I wanted things to be... During my brake adjusting procedure I found that the street side rear brake magnet wire was worn through after the retaining clips had fallen off the drag link allowing the wire to rub against the inner hub and ultimately wearing it through... I repaired this and continued on...

I also found that when they (Skyline) assembled the TT, they used Scotchlok connectors to tap the main brake wire for all the brakes... Scotchlok's are great for certain applications but NOT high current brake applications... In general, it was a VERY poor wiring job (not the first I have found on this TT!!) I rewired the existing brake circuit before our recent trip to Florida and took the TT for a test ride... Several very firm brake applications of truck and trailer revealed much better braking performance but I was still not satisfied...

I had recently read the article on the Hensley web site that dealt with Hensley rewiring a TT for testing with their new brake controller... The article made sense to me particularly with regard to the larger diameter wire... If you haven't read it yet, I suggest you do - it is quite informative...

I went on the Internet and purchased some 10 gauge wire from a Marine Supply Company - it's nice and flexible and wasn't real costly... I then proceeded to rewire the trailer last Saturday with the 10 gauge wire and soldering ALL connections from the trailer plug junction box all the way back to each individual brake magnet... I used heat shrink tubing on all connections at the brakes and electrical tape for the junctions of the 10 gauge wire...

The original trailer brake wiring path was down the street side of the trailer frame and then running across the axles to the other set of brakes... When Hensley rewired theirs, they ran down the center of the TT and branched equally to each brake assembly from the center main feed... While in theory, the slightly longer length of wire from one side to another shouldn't make any difference, I decided to wire the TT the way they did it if nothing else , for symmetry...

Below are pictures of the wire used versus the wire I removed... I haven't had a chance to check brake performance yet but I suspect it will be better than before... Just how much better remains to be seen and I'll report back on that after I test it in 2 weeks when I'm out at the local CG again...

I'll take a few more pictures of the installation and post them after the driveway drys out a bit... It just rained here and it's a bit damp to be crawling under the TT taking pictures...

Have you checked for oil or grease in the brakes?

Most two axle trailer brakes will draw about 1 amp per volt applied.

The voltage drop indicates high resistance. Think of a screen, clean water will pass through easily dirty it slows down same with electricity. You need to redo all of your connections.

Just outside of the brake drum is where the magnet connects to the wiring. Since these may at some point need replacing just clean them with a spray electrical cleaner and twist securely. You could trim a inch or two off the wire from the axle if needed. They almost always have a bit of extra wire stuffed inside the axle. Maybe put some heat shrink tubing over the connection instead of tape but tape will do if it's all you have on hand. Where the multiple wires join I like to solder them for a trouble free connection. You won't be able to heat shrink these but I've not had any trouble with electrical tape on soldered joints.

I like to tape the wire where in enters and leaves the axle. Put on enough tape so you have to force it into the hole. This will keep it from chaffing. You may even have to redo the plug that goes into the TV. A couple of hours work should give you years of trouble free service.

Each magnet should be drawing 3-3.8 amps, about 12-15 amps for the circuit.

What brake controller are you using and how are you measuring the current?

I have had trouble with the wires that go through the axles getting shorted out. I ran a wire on the outside of the axle and improved braking a lot. Make sure all your connections are good and clean and the brakes are adjusted properly.

Have you been towing this trailer for a while? Were the brakes stronger at one point. With heavier trailers, the brakes do not grab and stop like light single axle trailers.
How do the brakes grab when not using for the truck brakes and fully engaging the slide switch on the controller?
You can also check the voltage at the truck 7 pin connector as you are engaging the brake controller. If voltage is good there and not at the brakes, this should isolate the problem to the trailer wiring.

Have you adjusted the brakes lately?

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